1. Field of the Invention
This invention relates to the fields of video imaging and image processing.
2. Description of Related Art
The field of video imaging has developed along parallel paths, producing one mode of representation for imaging of video signals in a broadcast context (e.g. the broadcast standards NTSC and PAL), and another quite different mode of representation for imaging of video signals in a computer graphics context (e.g. RGB, the separation of a video signal into red, green and blue components). Major differences between these two modes of representation include amount of resolution and timing requirements. The first mode of representation is dominant in the field of broadcast video imaging, such as commercial television and videotape recording, while the second mode of representation is dominant in the field of computer graphics, such as digital image creation, CAD/CAM and computer monitor display. The advancing state of computer graphics has lead to a strong demand for the capability to transfer images rom a computer graphics context to a broadcast video context, retaining the highest possible image resolution and at reasonable cost, while simultaneously flexibly allowing conversion of differences between standards such as aspect ratio and resolution.
One method for converting images from graphics format to broadcast format is to display the graphics video signal on a color computer monitor and to point a video camera at the monitor, taking a broadcast format signal from the output of the video camera. While this method will convert from one format to the other, it is subject to a number of problems, including those of image alignment and synchronization of the camera with the monitor. It is also generally necessary to resynchronize the camera and image for each conversion session, with the result that image details will tend to drift over the duration of a long motion picture.
A second method for converting images from graphics format to broadcast format is to digitally remove information from an input graphics signal and filter the result to produce an output broadcast format signal. Information may typically be removed by removing periodic horizontal scan lines of input, e.g. every other line or every third line. While this method will convert from one format to the other, it is subject to a number of problems. For example, this method is unable to convert aspect ratio, except in certain special cases, and this method tends to distort or lose small area features of the input image, such as fine lines and small size lettering.
Accordingly, it is an object of the invention to provide a method for converting a high-resolution graphics image signal to a broadcast image signal, retaining the highest possible image resolution and at reasonable cost, while simultaneously allowing conversion of differences between modes of representation such as aspect ratio and resolution. This object, as well as other and further objects of the invention, will be apparent after examination of the specification, the drawings, and the claims herein.